Antibodies to Heat Shock Proteins - Product Review 03

Introduction

Heat shock proteins or HSPs are being synthesized under different kind of stress conditions and act as molecular chaperones for protein molecules.

Because these proteins were first found in cells that were exposed to high temperatures, they are called "heat shock proteins" and have been named according to their molecular weights.

Usually HSPs are cytoplasmic proteins and they function in various intra-cellular processes. Heat shock proteins play an important role in protein-protein interactions, including folding and assisting in establishing of proper protein conformation, and prevention of inappropriate protein aggregation.

Heat Shock Protein 20 (HSP20)

The HSP20 was demonstrated to constitute up to 1.3 % of the total cellular protein in vertebrate tissues, especially in muscle, and its expression is related to muscle contraction, specifically in slow-twitch muscle. HSP20 may form different heterocomplexes with other HSPs, such as alphaB-crystalline and HSP25. Phosphorylated form of HSP20 is proposed to interact with monomeric actin whereas dephosphorylated form binds polymeric actin filaments. In normal conditions HSP20 is diffusely disturbed in cytosol but under the heat stress it undergoes translocation to membrane fraction.

Heat Shock Protein 25/27 (HSP25/27)

Small heat shock proteins are a group of 15-30 kDa sized homologous proteins. HSP25/27 is constitutively expressed in different tissues and its concentration may reach 20-40 mg per 100 g of tissue wet weight. HSP25/27 is localized in the cytosol under unstressed conditions, and translocates inside the nucleus during the stress. The amino acid sequence homology between HSP25 (e.g. mouse) and HSP27 (human) is over 80 %. In living cell HSP25/27 is represented as an equilibrium mixture of monomers and oligomers with MW from 140 to 800 kDa. Heat stress shifts the equilibrium towards oligomers, whereas phosphorylation induces dissociation of large oligomers and decrease of its chaperone activity. The major functions of HSP25/27 include stabilization of microfilaments, and cytokine signal transduction. HSP25/27 interacts with the barbed ends of actin filaments and is considered to be an inhibitor of actin polymerization.

Heat Shock Protein 60 (HSP60)

The representatives of HSP60 subfamily are found in bacteria, plant chloroplasts and mitochondria of animal cells. Together with other HSPs, HSP60 is participating in reactivation of heat-denatured proteins. In muscle tissues HSP60 facilitates the folding and assembly of proteins as they enter the mitochondria, and stabilizes preexisting proteins under stress conditions. HSP60 is constitutively expressed in muscle in proportion to the mitochondrial content, and is increased after chronic electrical stimulation or prolonged endurance training, corresponding with increased mitochondrial enzyme activity.

Heat shock proteins have been proved to be greatly involved in many autoimmune diseases. Increased HSP60 concentration is observed in the blood of patients with carotid atherosclerosis or borderline hypertension.

The HSP70 family is a set of highly conserved proteins that are induced by a variety of biological stresses, including heat stress, in every organism in which the proteins have been examined. The human HSP70 family members include: HSP70, a 70 kDa protein which is strongly inducible in all organisms but which is also constitutively expressed in primate cells; HSP72, a 72 kDa protein which is induced exclusively under stress conditions; HSC70, or cognate protein, is a 72 kDa constitutively expressed protein which is involved in uncoating clathrin-coated vesicles; GRP78, or BiP, is a glucose- regulated 78 kDa protein localized to the endoplasmic reticulum; and mitochondrial HSP70 (mtHSP70, GRP75 or mortalin) a 75 kDa protein that is found within the mitochondria.

The HSP90 family consists of HSP90a, HSP90ß and GPR94. The HSP105 (also called HSP110) family is composed of HSP105, Apg-1 and Apg-2.

Antibody Tools for the Detection of Heat Shock Proteins

Acris Antibodies offers a broad range of antibodies to HSPs, which can be used in various immunological detection methods like Western blot, immunofluorescence, immunohistochemistry and others. More informations like host, isotype, species cross-reactivity etc. are shown in table 1.